This invention relates to arresting the forward motion of vehicles, such as aircraft overrunning a runway, and more particularly to arresting embodiments with improved resistance to jet blast and other potentially destructive forces.
The problem of aircraft overrunning the ends of runways, with the possibility of passenger injury and aircraft damage, is discussed in U.S. Pat. No. 5,885,025, “VEHICLE ARRESTING BED SYSTEMS” (which may be referred to as “the '025 patent”). That patent, together with U.S. Pat. No. 5,902,068, “VEHICLE ARRESTING UNIT FABRICATION METHOD” (the '068 patent) and U.S. Pat. No. 5,789,681, “ARRESTING MATERIAL TEST APPARATUS AND METHODS” (the '681 patent) describe arresting beds, units and fabrication methods, and testing based on application of cellular concrete for arresting purposes. The disclosures of the '025, '068 and '681 patents are hereby incorporated herein by reference.
By way of example, FIGS. 1A, 1B and 1C provide top, side and end views of a vehicle arresting bed constructed of cellular concrete blocks for installation at the end of an airport runway. As more fully described in the '025 patent, an overrunning aircraft enters the bed via a sloped ramp and encounters an array of cellular concrete blocks of increasing height and compressive gradient strength. Such compressive gradient strengths and the bed geometry are predetermined to enable forward travel to be arrested, while minimizing the potential for passenger injury and aircraft damage. In these figures, vertical dimensions and individual block size are expanded for clarity. An actual arresting bed may have dimensions of the order of 150 feet in width, with a maximum height or thickness of 30 inches, and include thousands of blocks of four foot by four foot or four foot by eight foot horizontal dimensions.
Arresting beds constructed pursuant to the above patents, with installations at major airports, have been shown to be effective in safely stopping aircraft under actual emergency overrun conditions. For example, the arresting of an overrunning airliner at JFK International Airport by an arresting bed fabricated by the assignee of the present invention, was reported in the New York Times of May 13, 1999. However, in some applications, depending in part upon particular airport layout, the proximity of jet blast or other physical forces may give rise to deteriorating or destructive effects which could limit the useful life of an arresting bed. Material such as cellular concrete, when used in an arresting bed, must have limited strength to permit compressive failure of the concrete without destruction of the landing gear of an aircraft, for example. Thus, the requirement to limit the strength of compressible material used for arresting purposes, in turn may make the material susceptible to damage or destruction by sonic, pressure, vibrational, lift, projected gravel and other characteristics and effects of jet blast from nearby aircraft, as well as from other sources, such as objects, people or vehicles making contact with an arresting bed other than during actual arresting incidents. As to jet blast phenomena in particular, measured conditions at an end-of-runway arresting bed installation site have included wind velocities to 176 MPH and 150 dB or higher sonic levels.
Accordingly, objects of the present invention are to provide new and improved arresting blocks and beds, and methods relating thereto, which may have one or more of the following characteristics and capabilities:
predetermined performance during aircraft arrestment;
improved resistance to some or all jet blast phenomena;
improved resistance to damage from pedestrian and maintenance vehicle traffic;
improved durability in installations in close proximity to aircraft operations;
improved resistance to atmospheric conditions;
simplified installation and replacement; and
improved resistance to damage during shipment and installation.